残差

收敛监测的残差图

在计算过程中，显示残差图（见图 Diagram of Iterations and Residuals )RWIND 3。 It is a logarithmic chart that is also available for inspection after the calculation.

The graph illustrates the progress of the applied residual quantity during the iterative simulation process. Starting from an initial value of the residual quantity, the simulation refines the residuals with every iteration, trying to reduce the imbalance of the residual in the finite volume. The lower the residuals become, the more accurate the solution will be. The simulation terminates when the convergence criterion or the maximum number of iterations has been reached (note that no less than 300 iterations are always carried out). Thus, the residuals represents an important tool to judge the convergence of the simulation.

The residual graphs for monitoring the convergence of the numerical solution have been extended with additional quantities, namely the components of the force Fx, Fy, Fz residuals acting on the primary model and the components of the velocity Vx, Vy, Vz residuals.

残差图用于监测收敛情况

您可以通过在“模拟参数”对话框中的设置来控制迭代计算（见章节 模拟参数）。

To resize the "Graph of residuals and iterations," move the window frames accordingly.

Use the button to print the diagram. The "Windows Print" dialog box appears where you can
specify the printer and its settings.

When you click the button, the "Graph Settings" dialog box is opened. There, you can adjust the
layout of the "Curves," for example.

图形设置

如果“残差”图显示出任何与收敛有关的问题，则应检查 模拟参数（网格密度、收敛准则）和 风洞。 For the latter, the default size is set as small as possible to obtain short calculating times. If its length in the X-direction is too short (especially the area behind the object), effects of divergence and, thus, oscillating values of residual pressure may arise. In that case, extend the wind tunnel accordingly. 详细信息参见章节 故障排除 。 In specific cases, however, oscillating results are correct when they are within a consistent bandwidth without increasing. 这种效应在圆柱模型的模拟中得到了说明 YouTube 和 FAQ 4731 。